Cable-type secondary battery

ABSTRACT

The present disclosure provides a cable-type secondary battery, comprising: an inner electrode supporter; and a sheet-form laminate of inner electrode-separation layer-outer electrode, spirally wound on the outer surface of the inner electrode supporter, wherein the laminate of inner electrode-separation layer-outer electrode is formed by carrying out compression for the integration of an inner electrode, a separation layer for preventing a short circuit, and an outer electrode. In the cable-type secondary battery of the present disclosure, since the electrodes and the separation layer are adhered to each other and integrated, the separation layer coming into contact with the electrodes absorbs an electrolyte solution to induce the uniform supply of the electrolyte solution into the outer electrode active material layer, thereby enhancing the stability and performances of the cable-type secondary battery.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application No.PCT/KR2014/004042 filed on May 7, 2014, which claims priority under 35USC 119(a) to Korean Patent Application No. 10-2013-0051561 filed in theRepublic of Korea on May 7, 2013, and Korean Patent Application No.10-2014-0054275 filed in the Republic of Korea on May 7, 2014, thedisclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a cable-type secondary battery whichcan freely change in shape, and more specifically to a cable-typesecondary battery constructed to comprise an inner electrode supporter,and an integrated laminate of electrodes and a separation layer.

BACKGROUND ART

Secondary batteries are devices capable of storing energy in chemicalform and of converting into electrical energy to generate electricitywhen needed. The secondary batteries are also referred to asrechargeable batteries because they can be recharged repeatedly. Commonsecondary batteries include lead accumulators, NiCd batteries, NiMHaccumulators, Li-ion batteries, Li-ion polymer batteries, and the like.When compared with disposable primary batteries, not only are thesecondary batteries more economically efficient, they are also moreenvironmentally friendly.

Secondary batteries are currently used in applications requiring lowelectric power, for example, equipment to start vehicles, mobiledevices, tools, uninterruptible power supplies, and the like. Recently,as the development of wireless communication technologies has beenleading to the popularization of mobile devices and even to themobilization of many kinds of conventional devices, the demand forsecondary batteries has been dramatically increasing. Secondarybatteries are also used in environmentally friendly next-generationvehicles such as hybrid vehicles and electric vehicles to reduce thecosts and weight and to increase the service life of the vehicles.

Generally, secondary batteries have a cylindrical, prismatic, or pouchshape. This is associated with a fabrication process of the secondarybatteries in which an electrode assembly composed of an anode, acathode, and a separator is mounted in a cylindrical or prismatic metalcasing or a pouch-shaped casing of an aluminum laminate sheet, and inwhich the casing is filled with electrolyte. Because a predeterminedmounting space for the electrode assembly is necessary in this process,the cylindrical, prismatic or pouch shape of the secondary batteries isa limitation in developing various shapes of mobile devices.Accordingly, there is a need for secondary batteries of a new structurethat are easily adaptable in shape.

To fulfill this need, suggestions have been made to develop cable-typebatteries having a very high ratio of length to cross-sectionaldiameter. Korean Patent Application publication No. 2005-99903 disclosesa flexible battery consisting of an inner electrode, an outer electrodeand an electrolyte layer interposed therebetween. However, such batteryhas poor flexibility. The linear batteries use a polymer electrolyte toform an electrolyte layer, but this causes difficulties in the inflow ofthe electrolyte into an electrode active material, thereby increasingthe resistance of the batteries and deteriorating the capacity and cyclecharacteristics thereof.

Also, the cable-type batteries may have spaces that are ununiformlygenerated among a separation layer interposed between an inner electrodeand an outer electrode and such electrodes in the preparation thereof,and such a space may disturb the introduction of an electrolyte solutionin an outer electrode active material layer, thereby deterioratingbattery performances.

In addition, in the case of cable-type batteries having a wire-formcurrent collector, since a value of line resistance is generally higherthan that of sheet resistance, the wire-form current collector mayexhibit high resistance as compared with a sheet-form current collector,thereby deteriorating battery performances.

SUMMARY OF THE DISCLOSURE

The present disclosure is designed to solve the problems of the relatedart, and therefore the present disclosure is directed to providing asecondary battery having a new linear structure, which can easily changein shape, maintain excellent stability and performances as a secondarybattery, and facilitate the inflow of an electrolyte into an electrodeactive material.

In accordance with one aspect of the present disclosure, there isprovided a cable-type secondary battery, comprising: an inner electrodesupporter; and a sheet-form laminate of inner electrode-separationlayer-outer electrode, spirally wound on the outer surface of the innerelectrode supporter, wherein the laminate of inner electrode-separationlayer-outer electrode is formed by carrying out compression for theintegration of an inner electrode, a separation layer for preventing ashort circuit, and an outer electrode.

At this time, the sheet-form laminate of inner electrode-separationlayer-outer electrode may have a strip structure extending in onedirection.

In addition, the sheet-form laminate of separation layer-outer electrodemay be spirally wound so that it is not overlapped in its width or sothat it is overlapped.

The laminate of inner electrode-separation layer-outer electrode may beformed by maintaining a peel strength of 15 to 300 N/m between the innerelectrode and the separation layer or between the separation layer andthe outer electrode during compression for the integration thereof.

In accordance with another aspect of the present disclosure, there isprovided a cable-type secondary battery, comprising: an inner electrodesupporter; a sheet-form inner electrode spirally wound on the outersurface of the inner electrode supporter; and a sheet-form laminate ofseparation layer-outer electrode, spirally wound on the outer surface ofthe inner electrode, wherein the laminate of separation layer-outerelectrode is formed by carrying out compression for the integration of aseparation layer for preventing a short circuit, and an outer electrode.

At this time, the sheet-form laminate of separation layer-outerelectrode may have a strip structure extending in one direction.

In addition, the sheet-form laminate of separation layer-outer electrodemay be spirally wound so that it is not overlapped in its width or sothat it is overlapped.

The laminate of separation layer-outer electrode may be formed bymaintaining a peel strength of 15 to 300 N/m between the separationlayer and the outer electrode during compression for the integrationthereof.

In accordance with another aspect of the present disclosure, there isprovided a cable-type secondary battery, comprising: an inner electrodesupporter; a sheet-form laminate of inner electrode-separation layer,spirally wound on the outer surface of the inner electrode supporter;and a sheet-form outer electrode wound on the outer surface of thelaminate of inner electrode-separation layer, wherein the laminate ofinner electrode-separation layer is formed by carrying out compressionfor the integration of an inner electrode and a separation layer forpreventing a short circuit.

At this time, the sheet-form laminate of inner electrode-separationlayer may have a strip structure extending in one direction.

In addition, the sheet-form laminate of inner electrode-separation layermay be spirally wound so that it is not overlapped in its width or sothat it is overlapped.

The laminate of inner electrode-separation layer may be formed bymaintaining a peel strength of 15 to 300 N/m between the inner electrodeand the separation layer during compression for the integration thereof.

The inner electrode supporter may have an open structure, and the innerelectrode supporter may be in the form of a hollow fiber, a wound wire,a wound sheet or a mesh.

The hollow fiber may be obtained from at least one selected from thegroup consisting of polyethylene, polypropylene,polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile,polyimide, polyethylene terephthalate, polyamide imide, polyester imide,polyether sulfone, polysulfone and a mixture thereof.

Meanwhile, the inner electrode may comprise an inner current collectorand an inner electrode active material layer formed on a surface of theinner current collector, and wherein the outer electrode may comprise anouter current collector and an outer electrode active material layerformed on a surface of the outer current collector.

At this time, the cable-type secondary battery may further comprise apolymer film formed on another surface of the inner current collector orthe outer current collector.

Here, the polymer film may be made of any one selected from the groupconsisting of polyolefin, polyester, polyimide, polyamide and a mixturethereof.

In addition, the inner current collector or the outer current collectormay be in the form of a mesh.

In the present disclosure, the separation layer may have a size largerthan those of the inner current collector and the outer currentcollector in the width and the length thereof.

Also, at least one of the inner current collector and the outer currentcollector may further comprise a primer coating layer consisting of aconductive material and a binder.

At this time, the conductive material may comprise any one selected fromthe group consisting of carbon black, acetylene black, ketjen black,carbon fiber, carbon nanotube, graphene and a mixture thereof.

In addition, the binder may be selected from the group consisting ofpolyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polybutylacrylate, polymethyl methacrylate, polyacrylonitrile,polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate,polyethylene oxide, polyarylate, cellulose acetate, cellulose acetatebutyrate, cellulose acetate propionate, cyanoethylpullulan,cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose,pullulan, carboxylmethyl cellulose, styrene-butadiene rubber,acrylonitrile-styrene-butadiene copolymer, polyimide and a mixturethereof.

Meanwhile, the inner electrode may further comprise a polymer supportinglayer formed on the surface of the inner electrode active materiallayer.

At this time, the polymer supporting layer may be a porous layer havinga pore size of 0.01 to 10 μm and a porosity of 5 to 95%.

In addition, the polymer supporting layer may comprise a linear polymerwith polarity, an oxide-based linear polymer or a mixture thereof.

At this time, the linear polymer with polarity may be selected from thegroup consisting of polyacrylonitrile, polyvinyl chloride,polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polyethyleneimine, polymethyl methacrylate, polybutyl acrylate,polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate,polyarylate, poly-p-phenylene terephthalamide and a mixture thereof.

In addition, the oxide-based linear polymer may be selected from thegroup consisting of polyethylene oxide, polypropylene oxide,polyoxymethylene, polydimethylsiloxane and a mixture thereof.

In addition, the inner current collector or the outer current collectorconfigured in the form of a wound sheet may have a plurality of recesseson at least one surface thereof.

The plurality of recesses may be continuously patterned orintermittently patterned.

The inner current collector may be made of stainless steel, aluminum,nickel, titanium, sintered carbon, or copper; stainless steel treatedwith carbon, nickel, titanium or silver on the surface thereof; analuminum-cadmium alloy; a non-conductive polymer treated with aconductive material on the surface thereof; or a conductive polymer.

The conductive material used in the inner current collector may beselected from the group consisting of polyacetylene, polyaniline,polypyrrole, polythiophene, polysulfurnitride, indium tin oxide (ITO),silver, palladium, nickel and a mixture thereof.

The conductive polymer used in the inner current collector may beselected from the group consisting of polyacetylene, polyaniline,polypyrrole, polythiophene, polysulfurnitride and a mixture thereof.

In addition, the outer current collector may be made of stainless steel,aluminum, nickel, titanium, sintered carbon, or copper; stainless steeltreated with carbon, nickel, titanium or silver on the surface thereof;an aluminum-cadmium alloy; a non-conductive polymer treated with aconductive material on the surface thereof; a conductive polymer; ametal paste comprising metal powders of Ni, Al, Au, Ag, Pd/Ag, Cr, Ta,Cu, Ba or ITO; or a carbon paste comprising carbon powders of graphite,carbon black or carbon nanotube.

Meanwhile, the inner electrode supporter may be a hollow structure whosecentral part is empty.

At this time, the inner electrode supporter may comprise one or morewire-form inner electrode supporters being spirally wound or one or moresheet-form inner electrode supporters being spirally wound.

In addition, the inner electrode supporter may comprise two or morewire-form inner current collectors being spirally crossed with eachother.

In addition, the inner electrode supporter may be provided with a coreof inner current collector, a core for supplying lithium ions, whichcomprises an electrolyte, or a filling core therein.

At this time, the core for supplying lithium ions may comprise a gelpolymer electrolyte and a support and may further comprise a liquidelectrolyte and a porous carrier.

Meanwhile, the electrolyte which is used in the core for supplyinglithium ions may be selected from a non-aqueous electrolyte solutionusing ethylene carbonate (EC), propylene carbonate (PC), butylenescarbonate (BC), vinylene carbonate (VC), diethyl carbonate (DEC),dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl formate(MF), γ-butyrolactone (γ-BL), sulfolane, methyl acetate (MA) or methylpropionate (MP); a gel polymer electrolyte using PEO, PVdF, PVdF-HFP,PMMA, PAN, or PVAc; and a solid electrolyte using PEO, polypropyleneoxide (PPO), polyether imine (PEI), polyethylene sulphide (PES), orpolyvinyl acetate (PVAc).

The electrolyte may further comprise a lithium salt which may beselected from LiCl, LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆,LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li,(CF₃SO₂)₂NLi, lithium chloroborate, lower aliphatic lithium carbonate,lithium tetraphenylborate, and a mixture thereof.

Meanwhile, the inner electrode may be an anode or a cathode, and theouter electrode may be a cathode or an anode corresponding to the innerelectrode.

When the inner electrode is an anode and the outer electrode is acathode, the inner electrode active material may comprise an activematerial selected from the group consisting of natural graphite,artificial graphite, or carbonaceous material; lithium-titanium complexoxide (LTO), and metals (Me) including Si, Sn, Li, Zn, Mg, Cd, Ce, Niand Fe; alloys of the metals; an oxide (MeOx) of the metals; a complexof the metals and carbon; and a mixture thereof, and the outer electrodeactive material may comprise an active material selected from the groupconsisting of LiCoO₂, LiNiO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, LiNiMnCoO₂,LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂ (wherein M1 and M2 are eachindependently selected from the group consisting of Al, Ni, Co, Fe, Mn,V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independently anatomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5,0≦z<0.5, and x+y+z≦1), and a mixture thereof.

Alternatively, when the inner electrode is a cathode and the outerelectrode is an anode, the inner electrode active material may comprisean active material selected from the group consisting of LiCoO₂, LiNiO₂,LiMn₂O₄, LiCoPO₄, LiFePO₄, LiNiMnCoO₂,LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂ (wherein M1 and M2 are eachindependently selected from the group consisting of Al, Ni, Co, Fe, Mn,V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independently anatomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5,0≦z<0.5, and x+y+z≦1), and a mixture thereof, and the outer electrodeactive material may comprise an active material selected from the groupconsisting of natural graphite, artificial graphite, or carbonaceousmaterial; lithium-titanium complex oxide (LTO), and metals (Me)including Si, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of the metals;an oxide (MeOx) of the metals; a complex of the metals and carbon; and amixture thereof.

Meanwhile, the separation layer may be an electrolyte layer or aseparator.

The electrolyte layer may comprise an electrolyte selected from a gelpolymer electrolyte using PEO, PVdF, PMMA, PVdF-HFP, PAN, or PVAc; and asolid electrolyte using PEO, polypropylene oxide (PPO), polyether imine(PEI), polyethylene sulphide (PES), or polyvinyl acetate (PVAc).

The electrolyte layer may further comprise a lithium salt.

At this time, the lithium salt may be selected from the group consistingof LiCl, LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂,LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi, lithiumchloroborate, lower aliphatic lithium carbonate, lithiumtetraphenylborate, and a mixture thereof.

The separator may be a porous polymersubstrate made of apolyolefin-based polymer selected from the group consisting of ethylenehomopolymers, propylene homopolymers, ethylene-butene copolymers,ethylene-hexene copolymers, and ethylene-methacrylate copolymers; aporous substrate made of a polymer selected from the group consisting ofpolyesters, polyacetals, polyamides, polycarbonates, polyimides,polyether ether ketones, polyether sulfones, polyphenylene oxides,polyphenylene sulfides and polyethylene naphthalates; a porous polymersubstrate made of a mixture of inorganic particles and a binder polymer;or a separator having a porous coating layer formed on at least onesurface of the porous polymer substrate and comprising inorganicparticles and a binder polymer.

At this time, the porous polymer substrate may be a porous polymer filmsubstrate or a porous non-woven fabric substrate.

Meanwhile, the cable-type secondary battery may further comprise aprotection coating surrounding the outer surface of the outer electrode.

Here, the protection coating may be made of a polymer resin.

At this time, the polymer resin may comprise any one selected from thegroup consisting of PET, PVC, HDPE, an epoxy resin and a mixturethereof.

In addition, the protection coating may further comprise amoisture-blocking layer.

At this time, the moisture-blocking layer may be made of aluminum or aliquid-crystalline polymer.

Further, in accordance with yet still another aspect of the presentinvention, there is provided a cable-type secondary battery, comprising:a core for supplying lithium ions, which comprise an electrolyte; anopen-structured inner electrode supporter surrounding the outer surfaceof the core for supplying lithium ions; and a sheet-form laminate ofinner electrode-separation layer-outer electrode, spirally wound on theouter surface of the inner electrode, wherein the sheet-form laminate ofinner electrode-separation layer-outer electrode is formed by carryingout compression for the integration of an inner electrode having aninner current collector and an inner electrode active material layerformed on the surface of the inner current collector, a separation layerfor preventing a short circuit, and an outer electrode having an outercurrent collector and an outer electrode active material layer formed onthe surface of the outer current collector.

In addition, in accordance with yet still another aspect of the presentinvention, there is provided a cable-type secondary battery, comprising:a core for supplying lithium ions, which comprise an electrolyte; anopen-structured inner electrode supporter surrounding the outer surfaceof the core for supplying lithium ions; a sheet-form inner electrodespirally wound on the outer surface of the inner electrode supporter andhaving an inner current collector and an inner electrode active materiallayer formed on the surface of the inner current collector; and asheet-form laminate of separation layer-outer electrode, spirally woundon the outer surface of the inner electrode, wherein the sheet-formlaminate of separation layer-outer electrode is formed by carrying outcompression for the integration of a separation layer for preventing ashort circuit, and an outer electrode having an outer current collectorand an outer electrode active material layer formed on the surface ofthe outer current collector.

In addition, in accordance with yet still another aspect of the presentinvention, there is provided a cable-type secondary battery, comprising:a core for supplying lithium ions, which comprise an electrolyte; anopen-structured inner electrode supporter surrounding the outer surfaceof the core for supplying lithium ions; a sheet-form laminate of innerelectrode-separation layer, spirally wound on the outer surface of theinner electrode supporter; and a sheet-form outer electrode spirallywound on the outer surface of the laminate of inner electrode-separationlayer and having an outer current collector and an outer electrodeactive material layer formed on the surface of the outer currentcollector, wherein the sheet-form laminate of inner electrode-separationlayer is formed by carrying out compression for the integration of aninner electrode having an inner current collector and an inner electrodeactive material layer formed on the surface of the inner currentcollector, and a separation layer for preventing a short circuit.

In addition, in accordance with yet still another aspect of the presentinvention, there is provided a cable-type secondary battery, comprising:two or more inner electrode supporters arranged in parallel to eachother; two or more inner electrodes spirally wound on the outer surfaceof each inner electrode supporter; and a sheet-form laminate ofseparation layer-outer electrode, spirally wound on the outer surface ofthe inner electrodes, the laminate of separation layer-outer electrodebeing formed by carrying out compression for the integration of aseparation layer for preventing a short circuit, and an outer electrode.

In addition, in accordance with yet still another aspect of the presentinvention, there is provided a cable-type secondary, comprising: two ormore cores for supplying lithium ions, which comprise an electrolyte; anopen-structured inner electrode supporter surrounding the outer surfaceof each core for supplying lithium ions; two or more inner electrodesspirally wound on the outer surface of each inner electrode supporterand arranged in parallel to each other, each inner electrode having aninner current collector and an inner electrode active material layerformed on the surface of the inner current collector; and a sheet-formlaminate of separation layer-outer electrode, spirally wound on theouter surface of the inner electrodes, the laminate of separationlayer-outer electrode being formed by carrying out compression for theintegration of a separation layer for preventing a short circuit, and anouter electrode having an outer current collector and an outer electrodeactive material layer formed on the surface of the outer currentcollector.

Thus, in the cable-type secondary battery of the present disclosure,since the electrodes and the separation layer are adhered to each otherand integrated, the separation layer coming into contact with theelectrodes absorbs an electrolyte solution to induce the uniform supplyof the electrolyte solution into the outer electrode active materiallayer, thereby enhancing the stability and performances of thecable-type secondary battery.

In addition, the cable-type secondary battery of the present disclosureuses a sheet-form electrode with excluding a wire-form current collectorhaving high resistance, thereby decreasing the resistance of the batteryand eventually improving battery performances.

In addition, according to an embodiment of the present disclosure, sincethe core supplying lithium ion is disposed within an inner electrodesupporter having an open structure, the electrolyte of the core forsupplying lithium ions can be easily impregnated into an electrodeactive material layer, thereby facilitating the supply and exchange oflithium ions, and eventually providing superior capacity and cyclecharacteristics.

Further, the cable-type secondary battery of the present disclosure hasthe open-structured inner electrode supporter and the sheet-formlaminate of electrode-separation layer spirally wound in the form of aspring, thereby maintaining a linear shape and reducing stress fromexternal forces.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate preferred embodiments of thepresent invention and, together with the foregoing disclosure, serve toprovide further understanding of the technical spirit of the presentinvention. However, the present invention is not to be construed asbeing limited to the drawings.

FIGS. 1 and 2 show a sheet-form laminate of inner electrode-separationlayer-outer electrode according to an embodiment of the presentdisclosure.

FIGS. 3 and 4 show a sheet-form laminate of separation layer-outerelectrode according to an embodiment of the present disclosure.

FIGS. 5 and 6 show a sheet-form laminate of inner electrode-separationlayer according to an embodiment of the present disclosure.

FIG. 7 shows a sheet-form laminate of inner electrode-separationlayer-outer electrode according to an embodiment of the presentdisclosure.

FIG. 8 schematically shows an inner electrode supporter and a sheet-formlaminate of inner electrode-separation layer-outer electrode wound onthe outer surface of the supporter, according to an embodiment of thepresent disclosure.

FIG. 9 shows a cable-type secondary battery comprising an innerelectrode supporter and a sheet-form laminate of innerelectrode-separation layer-outer electrode according to an embodiment ofthe present disclosure.

FIG. 10 shows a cable-type secondary battery comprising an innerelectrode supporter and a sheet-form laminate of separation layer-outerelectrode according to an embodiment of the present disclosure.

FIG. 11 shows a cable-type secondary battery comprising an innerelectrode supporter and a sheet-form laminate of innerelectrode-separation layer according to an embodiment of the presentdisclosure.

FIG. 12 shows a cross-section of a cable-type secondary battery havingmultiple inner electrodes according to the present disclosure.

FIG. 13 is a graph showing a voltage profile to normal capacity duringcharging of cable-type secondary batteries prepared in the Example andthe Comparative Example of the present disclosure.

FIG. 14 is a graph showing a voltage profile to normal capacity duringdischarging of cable-type secondary batteries prepared in the Exampleand the Comparative Example of the present disclosure.

FIG. 15 is a graph showing the cycle life characteristics of cable-typesecondary batteries prepared in the Example and the Comparative Exampleof the present disclosure.

EXPLANATION OF REFERENCE NUMERALS

-   -   1, 110, 210, 310, 410: Core for supplying lithium ions    -   2, 120, 220, 320, 420: Inner electrode supporter    -   5: Outer electrode    -   7: Inner electrode    -   10, 130: Laminate of inner electrode-separation layer-outer        electrode    -   11, 21, 332: Outer current collector    -   12, 22, 331: Outer electrode active material layer    -   13, 23, 33: Separation layer    -   14, 34, 232, 432: Inner electrode active material layer    -   15, 35, 231, 431: Inner current collector    -   20, 230, 430: Laminate of separation layer-outer electrode    -   30, 330: Laminate of inner electrode-separation layer    -   100, 200, 300, 400: Cable-type secondary battery    -   140, 240, 340, 440: Protection coating

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Priorto the description, it should be understood that the terms used in thespecification and the appended claims should not be construed as limitedto general and dictionary meanings, but interpreted based on themeanings and concepts corresponding to technical aspects of the presentdisclosure on the basis of the principle that the inventor is allowed todefine terms appropriately for the best explanation.

Therefore, the description proposed herein is just a preferable examplefor the purpose of illustrations only, not intended to limit the scopeof the disclosure, so it should be understood that other equivalents andmodifications could be made thereto without departing from the spiritand scope of the disclosure.

Conventional cable-type secondary batteries have an electrolyte layerwhich is interposed between an inner electrode and an outer electrode.In order for the electrolyte layer to isolate the inner electrode fromthe outer electrode and prevent a short circuit, the electrolyte layeris required to be made of gel-type polymer electrolytes or solid polymerelectrolytes having a certain degree of mechanical properties. However,such gel-type polymer electrolytes or solid polymer electrolytes fail toprovide superior performances as a source for lithium ions, so anelectrolyte layer made of such should have an increased thickness so asto sufficiently provide lithium ions. Such a thickness increase in theelectrolyte layer widens an interval between the electrodes to causeresistance increase, thereby deteriorating battery performances.

In order to solve this problem, there is an attempt to provide a coresupplying lithium ion and comprising a lithium salt within an innerelectrode supporter having an open structure, so that the electrolyte ofthe core for supplying lithium ions can pass through the inner electrodesupporter to reach an inner electrode active material layer and an outerelectrode active material layer.

However, owing to the presence of uneven parts in the inner electrodesupporter, there are spaces between an inner electrode and a separationor between the separation layer and an outer electrode. In this case,the spaces may disturb the introduction of an electrolyte solution inthe inner or outer electrode active material layers. For this reason,secondary batteries have exhibited ununiform discharging behaviors,making it difficult to achieve the desired battery performances.

Accordingly, the present inventors have endeavored to solve such aproblem and the problem has overcome by providing a laminate consistingof an electrode and a separation layer being integrated by pre-adhesionin the batteries so as to uniformly maintain spaces between theelectrode and the separation layer, thereby allowing for the separationlayer coming into contact with an electrode active material layer toabsorb an electrolyte solution from the inner electrode and induce theuniform supply of the electrolyte solution into the outer electrodeactive material layer.

Meanwhile, if a wire-form current collector is used in batteries, sincea value of line resistance is generally higher than that of sheetresistance, the wire-form current collector may exhibit high resistanceas compared with a sheet-form current collector, thereby deterioratingbattery performances. However, the present invention uses a sheet-formcurrent collector as an inner current collector and an outer currentcollector, thereby decreasing the resistance of the battery andeventually improving battery performances.

A cable-type secondary battery according to an embodiment of the presentdisclosure includes an inner electrode supporter; and a sheet-formlaminate of inner electrode-separation layer-outer electrode, spirallywound on the outer surface of the inner electrode supporter, wherein thelaminate of inner electrode-separation layer-outer electrode is formedby carrying out compression for the integration of an inner electrode, aseparation layer for preventing a short circuit, and an outer electrode.

In addition, a cable-type secondary battery according to anotherembodiment of the present disclosure includes an inner electrodesupporter; a sheet-form inner electrode spirally wound on the outersurface of the inner electrode supporter; and a sheet-form laminate ofseparation layer-outer electrode, spirally wound on the outer surface ofthe inner electrode, wherein the laminate of separation layer-outerelectrode is formed by carrying out compression for the integration of aseparation layer for preventing a short circuit, and an outer electrode.

In addition, a cable-type secondary battery according to anotherembodiment of the present disclosure includes an inner electrodesupporter; a sheet-form laminate of inner electrode-separation layer,spirally wound on the outer surface of the inner electrode supporter;and a sheet-form outer electrode wound on the outer surface of thelaminate of inner electrode-separation layer, wherein the laminate ofinner electrode-separation layer is formed by carrying out compressionfor the integration of an inner electrode and a separation layer forpreventing a short circuit. Here, the term ‘spirally’ used herein refersto represent a helix shape that turns around at a certain area whilemoving, including general spring forms.

At this time, the sheet-form laminate of inner electrode-separationlayer-outer electrode, the sheet-form laminate of separation layer-outerelectrode, and the sheet-form laminate of inner electrode-separationlayer may have a strip structure extending in one direction.

In addition, the sheet-form laminate of inner electrode-separationlayer-outer electrode, the sheet-form laminate of separation layer-outerelectrode, and the sheet-form laminate of inner electrode-separationlayer may be spirally wound so that it is not overlapped in its width.At this time, each sheet-form laminate may be spirally wound with spacewithin the double length of its width so that it is not overlapped, inorder to prevent the performance of the battery from deteriorating.

In addition, the sheet-form laminate of inner electrode-separationlayer-outer electrode, the sheet-form laminate of separation layer-outerelectrode, and the sheet-form laminate of inner electrode-separationlayer may be spirally wound so that it is overlapped in its width. Atthis time, each sheet-form laminate may be spirally wound so that thewidth of its overlapped part is within 0.9 folds of the width of theeach sheet-form laminate, in order to suppress excessive increase of aninternal resistance of the battery.

Referring to FIGS. 1, 3 and 5, the laminate of an electrode and aseparation layer according to the present disclosure may be a laminate10 of inner electrode-separation layer-outer electrode formed bycarrying out compression for the integration of an outer electrode 5, aseparation layer 13 and an inner electrode 7; a laminate 20 ofseparation layer-outer electrode formed by carrying out compression forthe integration of an outer electrode 5 and a separation layer 23; or alaminate 30 of inner electrode-separation layer formed by carrying outcompression for the integration of a separation layer 33 and an innerelectrode 7.

More preferably, referring to FIGS. 2, 4 and 6, the laminate consistingof an electrode and a separation layer according to the presentdisclosure may be a laminate 10 of inner electrode-separationlayer-outer electrode formed by compressing an outer current collector11, an outer electrode active material layer 12, a separation layer 13,an inner electrode active material layer 14 and an inner currentcollector 15 for the integration thereof; a laminate 20 of separationlayer-outer electrode formed by compressing an outer current collector21, an outer electrode active material layer 22 and a separation layer23 for the integration thereof; or a laminate 30 of innerelectrode-separation layer formed by compressing a separation layer 33,an inner electrode active material layer 34 and an inner currentcollector 35 for the integration thereof.

More specifically, the laminate 10 of inner electrode-separationlayer-outer electrode may be formed by stacking the inner electrode, theseparation layer and the outer electrode which are slit in the lengthdirection thereof and laminating them by way of roll press.

When the electrode active material layer comprises a binder and theseparation layer is a separator comprising the binder and inorganicmixture, the binder of the electrode active material layer or the binderrelease from the separator may provide stronger adhesiveness in aninterface between the separation layer and the electrodes.

In the present disclosure, the laminate 10 of inner electrode-separationlayer-outer electrode may be formed by maintaining a peel strength of 15to 300 N/m between the inner electrode 7 and the separation layer 13 orbetween the separation layer 13 and the outer electrode 5 duringcompression for the integration thereof, the laminate 20 of separationlayer-outer electrode may be formed by maintaining a peel strength of 15to 300 N/m between the separation layer 23 and the outer electrode 5during compression for the integration thereof, and the laminate 30 ofinner electrode-separation layer may be formed by maintaining a peelstrength of 15 to 300 N/m between the inner electrode 7 and theseparation layer 33 during compression for the integration thereof. Wheneach peel strength satisfies such a range, an adequate adhesivenessbetween the separation layer and the electrodes can be obtained withoutseparation thereof, thereby achieving good integration of the separationlayer and the electrodes.

In conventional cable-type secondary batteries provided with aseparation layer, a sheet-form separation layer is generally formed bywinding on the outer surface of an inner electrode, and at this time,both boundaries of the separation layer may be overlapped with eachother, so overlapped areas and non-overlapped areas may be present inthe separation layer.

If the separation layer is wound without overlapping in both boundariesthereof, the boundaries of the separation layer may be detached when thecable-type secondary batteries are bent or twisted, from which the innerelectrode may come into contact with the outer electrode to cause ashort circuit. For the purpose of preventing this problem, if theseparation layer is wound so that both boundaries thereof areoverlapped, the thickness of the separation layer becomes increased tocause other problems, for example, the ionic conductivity of batteriesmay be reduced.

In contrast, the present invention uses the laminate of a separationlayer and an electrode being integrated by pre-adhesion. That is, such alaminate of separation layer-electrode layer can be used in a cable-typebattery to prevent an internal short circuit due to the contact of aninner electrode and an outer electrode because the separation layer andthe electrode can integrally move even though the cable-type battery isbent. As a result, the flexibility of the battery can be enhanced andthe separation layer is minimized from overlapping in both boundariesthereof, thereby providing good ionic conductivity and contributing tothe improvement of battery performances.

Furthermore, since the separation layer and the electrodes areintegrated according to the present disclosure, the separation layer canacts as a buffer against external stress applied to an electrode activematerial layer, thereby preventing the release of an electrode activematerial from the electrode current collector even though extremebending stress is applied to the electrodes.

For example, referring to FIGS. 7 and 8, a sheet-form laminate 10 ofinner electrode-separation layer-outer electrode may be formed bylaminating an inner electrode (not shown), a separation layer 13 and anouter electrode 11, 12 by way of compression for their integration, inwhich the separation layer 13 may be designed to have a size larger thanthose of the inner electrode (not shown) and the outer electrode 11, 12in the width and the length thereof, thereby preventing a short circuitbetween the inner electrode (not shown) and the outer electrode 11, 12.More specifically, a width difference (w1) and a length difference (w2)between the separation layer 13 and the inner electrode or outerelectrode may each be 0.1 mm or more.

Then, the sheet-form laminate 10 of inner electrode-separationlayer-outer electrode is wound on the outer surface of an innerelectrode supporter 12 surrounding a core for supplying lithium ions,thereby preparing a cable-type battery.

Meanwhile, the inner electrode supporter may have an open structure.

The term ‘an open-structure’ used herein means that a structure has anopen boundary surface through which a substance may be transferredfreely from the inside of the structure to the outside thereof.

In the present disclosure, the open-structured inner electrode supportermay be in the form of a hollow fiber, a wound wire, a wound sheet or amesh, and also the supporter may have pores on the surface thereof,allowing the free movement of an electrolyte solution into the innerelectrode active material layer and the outer electrode active materiallayer to provide good wetting.

The open-structured inner electrode supporter can maintain the linearshape of the cable-type secondary battery and can prevent the disruptionor deformation of the electrode structure, thereby ensuring theflexibility of the cable-type secondary battery.

The hollow fiber may be obtained from at least one selected from thegroup consisting of polyethylene, polypropylene,polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile,polyimide, polyethylene terephthalate, polyamide imide, polyester imide,polyether sulfone, polysulfone and a mixture thereof, throughconventional hollow fiber preparations.

Also, the wound inner electrode supporter may be in the form of a springmade of a polymer or a metal. The polymer may be one having goodchemical resistance to be not react with an electrolyte solution, andthe metal may be the same as a metal used in the inner current collectoror outer current collector which will be described below.

The inner electrode supporter may have a diameter of 0.1 to 10 mm andpores with a diameter of 100 nm to 10 μm on the surface thereof.

The inner electrode may comprise an inner current collector and an innerelectrode active material layer formed on a surface of the inner currentcollector, and the outer electrode may comprise an outer currentcollector and an outer electrode active material layer formed on asurface of the outer current collector.

At this time, a polymer film formed on another surface of the innercurrent collector or the outer current collector may be furtherprovided.

Here, the polymer film may be made of any one selected from the groupconsisting of polyolefin, polyester, polyimide, polyamide and a mixturethereof.

In addition, the outer current collector is in the form of a mesh.

If a wire-form current collector is used in the electrode of cable-typesecondary batteries, it is not suitable because it has a surface areasmaller than that of a wound sheet or a wound mesh, and is not favorablein terms of increased resistance factors, thereby deteriorating the ratecharacteristics of the battery over battery resistance during high-ratecharging and discharging.

Meanwhile, when cable-type secondary batteries are subject to externalforces by bending or twisting, an electrode active material layer may bereleased from a current collector. For this reason, large amounts ofbinder components are used in the electrode active material layer so asto provide flexibility in electrodes. However, large amounts of bindermay be easily peeled off owing to swelling by an electrolyte solution,thereby deteriorating battery performances.

Accordingly, for the purpose of improving adhesiveness between anelectrode active material layer and a current collector, at least one ofthe inner current collector and the outer current collector may furthercomprise a primer coating layer consisting of a conductive material anda binder.

At this time, the conductive material used in the conductive layer maycomprise any one selected from the group consisting of carbon black,acetylene black, ketjen black, carbon fiber, carbon nanotube, grapheneand a mixture thereof.

In addition, the binder may be selected from the group consisting ofpolyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polybutylacrylate, polymethyl methacrylate, polyacrylonitrile,polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate,polyethylene oxide, polyarylate, cellulose acetate, cellulose acetatebutyrate, cellulose acetate propionate, cyanoethylpullulan,cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose,pullulan, carboxylmethyl cellulose, styrene-butadiene rubber,acrylonitrile-styrene-butadiene copolymer, polyimide and a mixturethereof.

Meanwhile, the inner electrode may further comprise a polymer supportinglayer formed on the surface of the inner electrode active materiallayer.

In the case that the inner electrode active material layer furthercomprises a polymer supporting layer on the surface thereof, inaccordance with one embodiment of the present disclosure, it is possibleto prevent crack occurrence even when the cable-type secondary batteryis bent by external force. Thereby, the release of the inner electrodeactive material layer can be prevented to minimize the deterioration ofbattery performances. Furthermore, the polymer supporting layer may havea porous structure which allows good introduction of an electrolytesolution in the inner electrode active material layer, therebypreventing an electrode resistance rise.

In the present disclosure, the polymer supporting layer may comprise alinear polymer with polarity, an oxide-based linear polymer or a mixturethereof.

The linear polymer with polarity may be selected from the groupconsisting of polyacrylonitrile, polyvinyl chloride, polyvinylidenefluoride (PVDF), polyvinylidene fluoride-co-hexafluoro propylene,polyvinylidene fluoride-co-trichloroethylene, polyethylene imine,polymethyl methacrylate, polybutyl acrylate, polyvinylpyrrolidone,polyvinylacetate, polyethylene-co-vinyl acetate, polyarylate,poly-p-phenylene terephthalamide and a mixture thereof.

The oxide-based linear polymer may be selected from the group consistingof polyethylene oxide, polypropylene oxide, polyoxymethylene,polydimethylsiloxane and a mixture thereof.

Also, the polymer supporting layer may be a porous layer having a poresize of 0.01 to 10 μm and a porosity of 5 to 95%.

Such a porous structure of the polymer supporting layer may be formed byphase separation or phase change using a non-solvent during itspreparation.

For example, polyvinylidene fluoride-co-hexafluoro propylene as apolymer is added to acetone used as a solvent to obtain a solutionhaving 10 wt % of solids. To the solution obtained, water or ethanol asa non-solvent is added in an amount of 2 to 10 wt % to formphase-separated parts of the non-solvent and the polymer.

Among these, the parts of the non-solvent become pores. Accordingly, thesize of pores can be controlled depending on the solubility of thenon-solvent and the polymer and the amount of the non-solvent.

Also, the inner current collector and the outer current collectorconfigured in the form of a wound sheet may have a plurality of recesseson at least one surface thereof so as to more increase its surface area.The recesses may be continuously patterned or intermittently patterned.That is, continuous patterned recesses may be formed with spacing apartwith each other in the longitudinal direction, or a plurality of holesmay be formed in the form of intermittent patterns. The plurality ofholes may be a circular or polygonal shape.

Meanwhile, the inner current collector may be made of stainless steel,aluminum, nickel, titanium, sintered carbon, or copper; stainless steeltreated with carbon, nickel, titanium or silver on the surface thereof;an aluminum-cadmium alloy; a non-conductive polymer treated with aconductive material on the surface thereof; or a conductive polymer.

Such a current collector serves to collect electrons generated byelectrochemical reaction of the active material or to supply electronsrequired for the electrochemical reaction. In general, the currentcollector is made of a metal such as copper or aluminum. Especially,when the current collector is made of a non-conductive polymer treatedwith a conductive material on the surface thereof or a conductivepolymer, the current collector has a relatively higher flexibility thanthe current collector made of a metal such as copper or aluminum. Also,a polymer current collector may be used instead of the metal currentcollector to reduce the weight of the battery.

The conductive material may include polyacetylene, polyaniline,polypyrrole, polythiophene, polysulfurnitride, indium tin oxide (ITO),silver, palladium, nickel, etc. The conductive polymer may includepolyacetylene, polyaniline, polypyrrole, polythiophene,polysulfurnitride, etc. However, the non-conductive polymer used for thecurrent collector is not particularly limited to its kinds.

In addition, the outer current collector of the present disclosure maybe made of stainless steel, aluminum, nickel, titanium, sintered carbon,or copper; stainless steel treated with carbon, nickel, titanium orsilver on the surface thereof; an aluminum-cadmium alloy; anon-conductive polymer treated with a conductive material on the surfacethereof; a conductive polymer; a metal paste comprising metal powders ofNi, Al, Au, Ag, Pd/Ag, Cr, Ta, Cu, Ba or ITO; or a carbon pastecomprising carbon powders of graphite, carbon black or carbon nanotube.At this time, the conductive material and the conductive polymer may bemade of the same material as those employed in the inner currentcollector described above.

Meanwhile, the inner electrode supporter may be a hollow structure whosecentral part is empty.

At this time, the inner electrode supporter comprised in the innerelectrode supporter may be one or more wires being spirally wound or oneor more sheets being spirally wound.

In addition, the inner electrode supporter may be two or more wiresbeing spirally crossed with each other.

In addition, the inner electrode supporter may be provided with a coreof the inner current collector therein.

At this time, the core of inner current collector may be made of carbonnanotube, stainless steel, aluminum, nickel, titanium, sintered carbon,or copper; stainless steel treated with carbon, nickel, titanium orsilver on the surface thereof; an aluminum-cadmium alloy; anon-conductive polymer treated with a conductive material on the surfacethereof; a conductive polymer.

In addition, the inner electrode supporter may be provided with a corefor supplying lithium ions, which comprises an electrolyte therein.

At this time, the core for supplying lithium ions may comprise a gelpolymer electrolyte and a support.

Also, the core for supplying lithium ions may comprise a liquidelectrolyte and a porous carrier.

In addition, the inner electrode supporter may be provided with afilling core therein.

The filling core may be made of several materials for improving variousperformances of cable-type batteries, for example polymer resins, rubberand inorganics, besides materials forming the core of inner currentcollector and the core for supplying lithium ions, and also may havevarious forms including wire, fiber, powder, mesh and foam.

Hereinafter, referring to FIGS. 9 to 11, a cable-type secondary battery100 according to an embodiment of the present invention comprises a core110 for supplying lithium ions, which comprises an electrolyte; anopen-structured inner electrode supporter 120 surrounding the outersurface of the core 110 for supplying lithium ions; and a sheet-formlaminate 130 of inner electrode-separation layer-outer electrode,spirally wound to surround the outer surface of the inner electrodesupporter 120, wherein the laminate 130 of inner electrode-separationlayer-outer electrode is formed by carrying out compression for theintegration of an inner electrode having an inner current collector andan inner electrode active material layer formed on the surface of theinner current collector, a separation layer for preventing a shortcircuit, and an outer electrode having an outer current collector and anouter electrode active material layer formed on the surface of the outercurrent collector.

Also, a cable-type secondary battery 200 according to another aspect ofthe present invention comprises a core 210 for supplying lithium ions,which comprises an electrolyte; an open-structured inner electrodesupporter 220 surrounding the outer surface of the core 210 forsupplying lithium ions; a sheet-form inner electrode spirally wound onthe outer surface of the inner electrode supporter 220 and having aninner current collector 231 and an inner electrode active material layer232 formed on the surface of the inner current collector; and asheet-form laminate 230 of separation layer-outer electrode, spirallywound on the outer surface of the inner electrode, wherein the laminate230 of separation layer-outer electrode is formed by carrying outcompression for the integration of a separation layer for preventing ashort circuit, and an outer electrode having an outer current collectorand an outer electrode active material layer formed on the surface ofthe outer current collector.

In addition, a cable-type secondary battery 300 according to stillanother aspect of the present invention comprises a core 310 forsupplying lithium ions, which comprises an electrolyte; anopen-structured inner electrode supporter 320 surrounding the outersurface of the core 310 for supplying lithium ions; a sheet-formlaminate 330 of inner electrode-separation layer, spirally wound on theouter surface of the inner electrode supporter 320; and a sheet-formouter electrode spirally wound on the outer surface of the laminate 330of inner electrode-separation layer and having an outer currentcollector 332 and an outer electrode active material layer 331 formed onthe surface of the outer current collector 332, wherein the laminate 330of inner electrode-separation layer is formed by carrying outcompression for the integration of an inner electrode having an innercurrent collector and an inner electrode active material layer formed onthe surface of the inner current collector and a separation layer forpreventing a short circuit.

The cable-type secondary battery of the present disclosure has ahorizontal cross section of a predetermined shape, a linear structure,which extends in the longitudinal direction, and flexibility, so it canfreely change in shape. The term ‘a predetermined shape’ used herein isnot limited to any particular shape, and refers to any shape that doesnot damage the nature of the present disclosure.

Meanwhile, the core 110, 210, 310 for supplying lithium ions comprisesan electrolyte which is not particularly limited to its kinds and may beselected from a non-aqueous electrolyte solution using ethylenecarbonate (EC), propylene carbonate (PC), butylenes carbonate (BC),vinylene carbonate (VC), diethyl carbonate (DEC), dimethyl carbonate(DMC), ethyl methyl carbonate (EMC), methyl formate (MF),γ-butyrolactone (γ-BL), sulfolane, methyl acetate (MA) or methylpropionate (MP); a gel polymer electrolyte using PEO, PVdF, PVdF-HFP,PMMA, PAN, or PVAc; and a solid electrolyte using PEO, polypropyleneoxide (PPO), polyether imine (PEI), polyethylene sulphide (PES), orpolyvinyl acetate (PVAc). Also, the electrolyte may further comprise alithium salt which may be selected from LiCl, LiBr, LiI, LiClO₄, LiBF₄,LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li,CF₃SO₃Li, (CF₃SO₂)₂NLi, lithium chloroborate, lower aliphatic lithiumcarbonate, lithium tetraphenylborate, and a mixture thereof. The core110, 210, 310 for supplying lithium ions may consist of only anelectrolyte, and especially a liquid electrolyte may be formed by usinga porous carrier.

In the present disclosure, the inner electrode may be an anode or acathode, and the outer electrode may be a cathode or an anodecorresponding to the inner electrode.

The electrode active material layers of the present disclosure allowions to move through the current collector, and the movement of ions iscaused by the interaction of ions such as intercalation/deintercalationof ions into and from the electrolyte layer.

Such electrode active material layers may be divided into an anodeactive material layer and a cathode active material layer.

Specifically, when the inner electrode is an anode and the outerelectrode is a cathode, the inner electrode active material layer maycomprise an anode active material selected from the group consisting ofnatural graphite, artificial graphite, or carbonaceous material;lithium-titanium complex oxide (LTO), and metals (Me) including Si, Sn,Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of the metals; an oxide (MeOx) ofthe metals; a complex of the metals and carbon; and a mixture thereof,and the outer electrode active material layer may comprise a cathodeactive material selected from the group consisting of LiCoO₂, LiNiO₂,LiMn₂O₄, LiCoPO₄, LiFePO₄, LiNiMnCoO₂,LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂ (wherein M1 and M2 are eachindependently selected from the group consisting of Al, Ni, Co, Fe, Mn,V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independently anatomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5,0≦z<0.5, and x+y+z≦1), and a mixture thereof.

Alternatively, when the inner electrode is a cathode and the outerelectrode is an anode, the inner electrode active material layer becomesa cathode active material layer and the outer electrode active materiallayer becomes an anode active material layer.

An electrode active material layer generally comprises an electrodeactive material, a binder and a conductive material and is combined witha current collector to construct an electrode. When the electrode issubject to deformation, e.g., folding or severe bending by externalforces, the electrode active material layer is released, therebydeteriorating battery performances and battery capacity. In contrast, inan electrode comprising the wound sheet-form outer current collector ofthe present disclosure, such a deformation is less induced because thewound sheet-form outer current collector has elasticity to disperse theexternal forces applied in the electrode. From this, the release of anactive material can be prevented.

In the present disclosure, the separation layer may be an electrolytelayer or a separator.

The electrolyte layer serving as an ion channel may be made of agel-type polymer electrolyte using PEO, PVdF, PVdF-HFP, PMMA, PAN orPVAc, or a solid electrolyte using PEO, polypropylene oxide (PPO),polyethylene imine (PEI), polyethylene sulfide (PES) or polyvinylacetate (PVAc). The matrix of the solid electrolyte is preferably formedusing a polymer or a ceramic glass as the backbone. In the case oftypical polymer electrolytes, the ions move very slowly in terms ofreaction rate, even when the ionic conductivity is satisfied. Thus, thegel-type polymer electrolyte which facilitates the movement of ions ispreferably used compared to the solid electrolyte. The gel-type polymerelectrolyte has poor mechanical properties and thus may comprise asupport. The support may be a porous support or a cross-linked polymerto improve poor mechanical properties. The electrolyte layer of thepresent invention can serve as a separator, and thus an additionalseparator may be omitted.

In the present disclosure, the electrolyte layer may further comprise alithium salt. The lithium salt can improve an ionic conductivity andresponse time. Non-limiting examples of the lithium salt may includeLiCl, LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂,LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi, lithiumchloroborate, lower aliphatic lithium carbonate, and lithiumtetraphenylborate.

Examples of the separator may include, but is not limited to, a porouspolymer substrate made of a polyolefin-based polymer selected from thegroup consisting of ethylene homopolymers, propylene homopolymers,ethylene-butene copolymers, ethylene-hexene copolymers, andethylene-methacrylate copolymers; a porous polymer substrate made of apolymer selected from the group consisting of polyesters, polyacetals,polyamides, polycarbonates, polyimides, polyether ether ketones,polyether sulfones, polyphenylene oxides, polyphenylene sulfides andpolyethylene naphthalates; a porous substrate made of a mixture ofinorganic particles and a binder polymer; or a separator having a porouscoating layer formed on at least one surface of the porous polymersubstrate and comprising inorganic particles and a binder polymer.

In the porous coating layer formed from inorganic particles and a binderpolymer, the inorganic particles are bound to each other by the binderpolymer (i.e., the binder polymer connects and immobilizes the inorganicparticles), and also the porous coating layer maintains the state ofbinding with the first supporting layer by the binder polymer, In such aporous coating layer, the inorganic particles are filled in contact witheach other, from which interstitial volumes are formed between theinorganic particles. The interstitial volumes between the inorganicparticles become empty spaces to form pores.

Among these, in order for the lithium ions of the core for supplyinglithium ions to be transferred to the outer electrode, it is preferredto use a non-woven fabric separator corresponding to the porous polymersubstrate made of a polymer selected from the group consisting ofpolyesters, polyacetals, polyamides, polycarbonates, polyimides,polyether ether ketones, polyether sulfones, polyphenylene oxides,polyphenylene sulfides and polyethylene naphthalates.

Also, the cable-type secondary battery of the present disclosure has aprotection coating. The protection coating acts as an insulator and isformed to surround the outer current collector, thereby protecting theelectrodes against moisture in the air and external impacts. Theprotection coating 140, 240, 340 may be made of conventional polymerresins having a moisture-blocking layer. The moisture-blocking layer maybe made of aluminum or a liquid-crystalline polymer which have goodwater-blocking ability, and the polymer resins may be PET, PVC, HDPE orepoxy resins.

Hereinafter, a cable-type secondary battery according to one embodimentof the present invention and the preparation thereof will be brieflyexplained with reference to FIG. 9.

A cable-type secondary battery 100 according to one embodiment of thepresent invention comprises a core 110 for supplying lithium ions, whichcomprises an electrolyte; an open-structured inner electrode supporter120 surrounding the outer surface of the core 110 for supplying lithiumions; and a sheet-form laminate 130 of inner electrode-separationlayer-outer electrode, spirally wound on the outer surface of the innerelectrode supporter 120, wherein the laminate 130 of innerelectrode-separation layer-outer electrode is formed by carrying outcompression for the integration of an inner electrode having an innercurrent collector and an inner electrode active material layer formed onthe surface of the inner current collector, a separation layer forpreventing a short circuit, and an outer electrode having an outercurrent collector and an outer electrode active material layer formed onthe surface of the outer current collector.

First, the core 110 for supplying lithium ions is obtained by providinga polymer electrolyte in the form of a wire using an extruder. Also, thecore 110 for supplying lithium ions may be formed by providing a hollowinner electrode supporter and introducing a non-aqueous electrolytesolution in the center of the inner electrode supporter, or may beformed by providing a battery assembly comprising a protection coatingand all and introducing a non-aqueous electrolyte solution in the centerof the inner electrode support comprised in the battery assembly.Alternatively, the core 110 for supplying lithium ions may be preparedby providing a wire-form carrier made of a sponge material andintroducing a non-aqueous electrolyte solution thereto.

Then, the wire-form inner electrode supporter 120 is provided and woundon the core 110 for supplying lithium ions.

Next, the sheet-form inner electrode and the sheet-form outer electrodeare obtained by forming an inner current electrode active material layerand an outer electrode active material layer by way of coating on asheet-form inner current collector and a sheet-form outer currentcollector, respectively. The coating may be carried out by conventionalcoating methods, for example, by an electroplating process or an anodicoxidation process. Also, it is preferable to carry out coating methodsin which an electrode slurry containing an active material is appliedthrough a comma coater or a slot die coater. In addition, the electrodeslurry containing an active material may be applied by way of dipcoating or extrusion-coating using an extruder.

Subsequently, the laminate 130 of inner electrode-separation layer-outerelectrode is formed by interposing a separation layer consisting of apolymer electrolyte layer between the sheet-form inner electrode and thesheet-form outer electrode, followed by lamination. At this time, amesh-form current collector may be used as the inner current collectorand the outer current collector.

Then, the laminate 130 of inner electrode-separation layer-outerelectrode thus formed is wound on the outer surface of the innerelectrode supporter 120 to obtain an electrode assembly, and theprotection coating 140 is formed to surround the outer surface of theelectrode assembly.

The protection coating 140 is an insulator and is formed on theoutermost surface for the purpose of protecting the electrodes againstmoisture in the air and external impacts. As the protection coating 140,conventional polymer resins, for example, PVC, HDPE and epoxy resins maybe used.

Hereinafter, another embodiment of the present disclosure will bebriefly explained.

A cable-type secondary battery according to one embodiment of thepresent invention comprises two or more inner electrode supportersarranged in parallel to each other; two or more inner electrodesspirally wound on the outer surface of each inner electrode supporter;and a sheet-form laminate of separation layer-outer electrode, spirallywound on the outer surface of the inner electrodes, the laminate ofseparation layer-outer electrode being formed by carrying outcompression for the integration of a separation layer for preventing ashort circuit, and an outer electrode.

Further, referring to FIG. 12, a cable-type secondary battery 400according to one embodiment of the present invention comprises two ormore cores 410 for supplying lithium ions, which comprise anelectrolyte; an open-structured inner electrode supporter 420surrounding the outer surface of each core 410 for supplying lithiumions; two or more inner electrodes spirally wound on the outer surfaceof each inner electrode supporter 420 and arranged in parallel to eachother, each inner electrode having an inner current collector 431 and aninner electrode active material layer 432 formed on the surface of theinner current collector 431; and a sheet-form assembly 430 of aseparation layer-an outer electrode, spirally wound on the outer surfaceof the inner electrodes, the assembly of a separation layer-an outerelectrode being formed by carrying out compression for the integrationof a separation layer for preventing a short circuit, and an outerelectrode having an outer current collector and an outer electrodeactive material layer formed on the surface of the outer currentcollector.

In the cable-type secondary battery 400 which has a plurality of innerelectrodes, the number of the inner electrodes can be adjusted tocontrol the loading amount of the electrode active material layers aswell as battery capacity, and a probability of short circuit can beprevented owing to the presence of multiple electrodes.

Hereinafter, the present invention will be described in detail throughspecific examples. However, the description proposed herein is just apreferable example for the purpose of illustrations only, not intendedto limit the scope of the invention, so it should be understood that theexamples are provided for a more definite explanation to an ordinaryperson skilled in the art.

EXAMPLE

Four Cu-wires having a diameter of 250 μm were wound with crossing witheach other to obtain an open-structured inner electrode supporter inwhich a hollow core for supplying lithium ions in the form of a springcan be present.

Then, 70 wt % of graphite as an anode active material, 5 wt % of Denkablack as a conductive material and 25 wt % of PVdF as a binder weremixed to obtain an anode active material-containing slurry. The slurrywas coated on a Cu-foil and slit into a piece with a width of 2 mm, toobtain a sheet-form inner electrode (anode).

Meanwhile, 80 wt % of LiCoO₂ as a cathode active material, 5 wt % ofDenka black as a conductive material and 15 wt % of PVdF were mixed toobtain a cathode active material-containing slurry. The slurry wascoated on an Al-foil and slit into a piece with a width of 2 mm, toobtain a sheet-form outer electrode (cathode).

Next, the sheet-form inner electrode was adhered with a sheet-formseparator consisting of a porous substrate obtained from inorganicparticles and a binder polymer, followed by lamination by using a rollpress, to obtain a sheet-form laminate of the inner electrode and theseparator being integrated by adhesion.

The laminate of the inner electrode and the separator thus obtained waswound on the outer surface of the open-structured inner electrodesupporter.

Subsequently, the sheet-form outer electrode was wound on the outersurface of the wound laminate of the inner electrode and the separator.Then, on the outer surface of the wound outer electrode, aheat-shrinkable tube having a moisture-blocking layer was applied andcontracted with heat, to form a protection coating layer.

Then, a non-aqueous electrolyte solution (1M LiPF₆, EC:PC=1:1 (volumeratio)) was introduced in the center of the inner electrode using asyringe, to form a core for supplying lithium ions, followed bycompletely sealing. Thereby, a cable-type secondary battery wasprepared.

Comparative Example

The procedures of Example 1 were repeated except that the sheet-forminner electrode was wound on the outer surface of the inner electrodesupporter and the separator was wound on the outer surface of the woundsheet-form inner electrode, instead of the step of wining the laminateof the inner electrode and the separator on the outer surface of theopen-structured inner electrode supporter, to prepare a cable-typesecondary battery.

Evaluation of Battery Performances

For the cable-type secondary batteries prepared in the Example and theComparative Example, 100 cycles of charge/discharge processes werecarried out with a current density of 0.3 C at a voltage condition of4.2 to 3.0 V, so as to confirm life characteristics and a voltageprofile to normal capacity.

FIGS. 13 and 14 are each a graph showing a voltage profile to normalcapacity during charging and discharging of cable-type secondarybatteries prepared in the Example and the Comparative Example of thepresent disclosure. From these, it was confirmed that the cable-typesecondary battery of the Example exhibited resistance decrease ascompared with the Comparative Example.

Also, FIG. 15 is a graph showing the cycle life characteristics ofcable-type secondary batteries prepared in the Example and theComparative Example of the present disclosure. From this, it wasconfirmed that the cable-type secondary battery of the Example exhibitedan increase in rate retention ratio, i.e., superior lifecharacteristics, as compared with the Comparative Example.

According to the results above, a laminate of a separation layer and anelectrode is applied in cable-type secondary batteries to minimizespaces between the electrode and the separation layer throughintegration, thereby improving the impregnation of an electrolytesolution into the micropores of the separation layer. From this, theresistance of the cable-type secondary batteries can decrease and thelife characteristics thereof can be improved.

APPLICABILITY TO THE INDUSTRY

The present disclosure has been described in detail. However, it shouldbe understood that the detailed description and specific examples, whileindicating preferred embodiments of the disclosure, are given by way ofillustration only, since various changes and modifications within thespirit and scope of the disclosure will become apparent to those skilledin the art from this detailed description.

What is claimed is:
 1. A cable-type secondary battery, comprising: aninner electrode supporter; and a sheet-form laminate of innerelectrode-separation layer-outer electrode, spirally wound on the outersurface of the inner electrode supporter, wherein the laminate of innerelectrode-separation layer-outer electrode is formed by carrying outcompression for the integration of an inner electrode, a separationlayer for preventing a short circuit, and an outer electrode, the innerelectrode comprises an inner current collector and an inner electrodeactive material layer formed on a surface of the inner currentcollector, and the outer electrode comprises an outer current collectorand an outer electrode active material layer formed on a surface of theouter current collector.
 2. The cable-type secondary battery accordingto claim 1, further comprising a polymer film formed on another surfaceof the inner current collector or the outer current collector.
 3. Thecable-type secondary battery according to claim 2, wherein the polymerfilm is made of any one selected from the group consisting ofpolyolefin, polyester, polyimide, polyamide and a mixture thereof. 4.The cable-type secondary battery according to claim 1, wherein the outercurrent collector is in the form of a mesh.
 5. The cable-type secondarybattery according to claim 1, wherein the inner electrode furthercomprises a polymer supporting layer formed on the surface of the innerelectrode active material layer.
 6. The cable-type secondary batteryaccording to claim 5, wherein the polymer supporting layer is a porouslayer having a pore size of 0.01 to 10 μm and a porosity of 5 to 95%. 7.The cable-type secondary battery according to claim 5, wherein thepolymer supporting layer comprises a linear polymer with polarity, anoxide-based linear polymer or a mixture thereof.
 8. The cable-typesecondary battery according to claim 7, wherein the linear polymer withpolarity is selected from the group consisting of polyacrylonitrile,polyvinyl chloride, polyvinylidene fluoride (PVDF), polyvinylidenefluoride-co-hexafluoro propylene, polyvinylidenefluoride-co-trichloroethylene, polyethylene imine, polymethylmethacrylate, polybutyl acrylate, polyvinylpyrrolidone,polyvinylacetate, polyethylene-co-vinyl acetate, polyarylate,poly-p-phenylene terephthalamide and a mixture thereof.
 9. Thecable-type secondary battery according to claim 7, wherein theoxide-based linear polymer is selected from the group consisting ofpolyethylene oxide, polypropylene oxide, polyoxymethylene,polydimethylsiloxane and a mixture thereof.
 10. The cable-type secondarybattery according to claim 1, wherein the separation layer has a sizelarger than those of the inner current collector and the outer currentcollector in the width and the length thereof.
 11. The cable-typesecondary battery according to claim 1, wherein at least one of theinner current collector and the outer current collector furthercomprises a primer coating layer consisting of a conductive material anda binder.
 12. The cable-type secondary battery according to claim 11,wherein the conductive material comprises any one selected from thegroup consisting of carbon black, acetylene black, ketjen black, carbonfiber, carbon nanotube, graphene and a mixture thereof.
 13. Thecable-type secondary battery according to claim 11, wherein the binderis selected from the group consisting of polyvinylidene fluoride (PVDF),polyvinylidene fluoride-co-hexafluoro propylene, polyvinylidenefluoride-co-trichloroethylene, polybutyl acrylate, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate,polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate,cellulose acetate, cellulose acetate butyrate, cellulose acetatepropionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol,cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxylmethylcellulose, styrene-butadiene rubber, acrylonitrile-styrene-butadienecopolymer, polyimide and a mixture thereof.
 14. The cable-type secondarybattery according to claim 1, wherein the inner current collector or theouter current collector being in the form of a wound sheet has aplurality of recesses on at least one surface thereof.
 15. Thecable-type secondary battery according to claim 14, wherein theplurality of recesses are continuously patterned or intermittentlypatterned.
 16. The cable-type secondary battery according to claim 15,wherein the continuously patterned recesses are spaced apart from eachother in the longitudinal direction.
 17. The cable-type secondarybattery according to claim 15, wherein the intermittently patternedrecesses are formed with a plurality of holes.
 18. The cable-typesecondary battery according to claim 17, wherein the plurality of holeshave a circular or polygonal shape.
 19. The cable-type secondary batteryaccording to claim 1, wherein the inner current collector is made ofstainless steel, aluminum, nickel, titanium, sintered carbon, or copper;stainless steel treated with carbon, nickel, titanium or silver on thesurface thereof; an aluminum-cadmium alloy; a non-conductive polymertreated with a conductive material on the surface thereof; or aconductive polymer.
 20. The cable-type secondary battery according toclaim 19, wherein the conductive material is selected from the groupconsisting of polyacetylene, polyaniline, polypyrrole, polythiophene,polysulfurnitride, indium tin oxide (ITO), silver, palladium, nickel anda mixture thereof.
 21. The cable-type secondary battery according toclaim 19, wherein the conductive polymer is selected from the groupconsisting of polyacetylene, polyaniline, polypyrrole, polythiophene,polysulfurnitride and a mixture thereof.
 22. The cable-type secondarybattery according to 1, wherein the outer current collector is made ofstainless steel, aluminum, nickel, titanium, sintered carbon, or copper;stainless steel treated with carbon, nickel, titanium or silver on thesurface thereof; an aluminum-cadmium alloy; a non-conductive polymertreated with a conductive material on the surface thereof; a conductivepolymer; a metal paste comprising metal powders of Ni, Al, Au, Ag,Pd/Ag, Cr, Ta, Cu, Ba or ITO; or a carbon paste comprising carbonpowders of graphite, carbon black or carbon nanotube.
 23. The cable-typesecondary battery according to claim 22, wherein the conductive materialis selected from the group consisting of polyacetylene, polyaniline,polypyrrole, polythiophene, polysulfurnitride, indium tin oxide (ITO),silver, palladium, nickel and a mixture thereof.
 24. The cable-typesecondary battery according to claim 22, wherein the conductive polymeris selected from the group consisting of polyacetylene, polyaniline,polypyrrole, polythiophene, polysulfurnitride and a mixture thereof. 25.A cable-type secondary battery, comprising: an inner electrodesupporter; and a sheet-form laminate of inner electrode-separationlayer-outer electrode, spirally wound on the outer surface of the innerelectrode supporter, wherein the laminate of inner electrode-separationlayer-outer electrode is formed by carrying out compression for theintegration of an inner electrode, a separation layer for preventing ashort circuit, and an outer electrode, the inner electrode being ananode or a cathode, and the outer electrode being a cathode or an anodecorresponding to the inner electrode.
 26. The cable-type secondarybattery according to claim 25, wherein when the inner electrode is ananode and the outer electrode is a cathode, the inner electrode activematerial comprises an active material selected from the group consistingof natural graphite, artificial graphite, or carbonaceous material;lithium-titanium complex oxide (LTO), and metals (Me) including Si, Sn,Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of the metals; an oxide (MeOx) ofthe metals; a complex of the metals and carbon; and a mixture thereof,and the outer electrode active material comprises an active materialselected from the group consisting of LiCoO₂, LiNiO₂, LiMn₂O₄, LiCoPO₄,LiFePO₄, LiNiMnCoO₂, LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂ (wherein M1 andM2 are each independently selected from the group consisting of Al, Ni,Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are eachindependently an atomic fraction of oxide-forming elements, in which0≦x<0.5, 0≦y<0.5, 0≦z<0.5, and x+y+z≦1), and a mixture thereof.
 27. Thecable-type secondary battery according to claim 25, wherein when theinner electrode is a cathode and the outer electrode is an anode, theinner electrode active material comprises an active material selectedfrom the group consisting of LiCoO₂, LiNiO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄,LiNiMnCoO₂, LiNi_(1-x-y-z)Co_(x)M1_(y)M2_(z)O₂ (wherein M1 and M2 areeach independently selected from the group consisting of Al, Ni, Co, Fe,Mn, V, Cr, Ti, W, Ta, Mg and Mo, and x, y and z are each independentlyan atomic fraction of oxide-forming elements, in which 0≦x<0.5, 0≦y<0.5,0≦z<0.5, and x+y+z≦1), and a mixture thereof, and the outer electrodeactive material comprises an active material selected from the groupconsisting of natural graphite, artificial graphite, or carbonaceousmaterial; lithium-titanium complex oxide (LTO), and metals (Me)including Si, Sn, Li, Zn, Mg, Cd, Ce, Ni and Fe; alloys of the metals;an oxide (MeOx) of the metals; a complex of the metals and carbon; and amixture thereof.